A semiconductor device such as a circuit board including semiconductor components such as thin film transistors (TFTs) has been widely used as a component of an electronic device such as a liquid crystal display device, an electroluminescent display device, and an electrophoretic display device.
Hereinafter, a circuit configuration of a TFT array board included in a liquid crystal panel that is driven with the TFTs will be described. Generally, the TFT array board includes a pixel circuit including m-lines of scanning lines and n-columns of signal lines and the TFTs that are switching components. The scanning lines and the signal lines are arranged in a matrix of m×n and the TFTs are arranged on intersections of the scanning lines and the signal lines, respectively. Drain electrodes of the TFTs are electrically connected to pixel electrodes. Peripheral circuits such as a scanning driver integrated circuit (IC) and a data driver IC are electrically connected to gate lines and source lines extending from the respective TFTs.
Operations of the circuits are generally influenced by performances of the TFTs that are disposed on the TFT array board. The performances of the TFTs disposed on the TFT array board vary according to materials thereof. Therefore, the TFTs disposed on the circuit influence whether the circuit can operates, whether a size of the circuit is increased, or whether a yield rate is decreased, and operations of the circuit disposed on the TFT array board are influenced thereby. Amorphous silicon (a-Si) has been widely used in the semiconductor devices (the circuit boards) because the TFTs are formed easily with a low cost.
A method of manufacturing a semiconductor device including oxide semiconductor films instead of including the amorphous silicon semiconductor films has been disclosed (for example, Patent Document 1).